This type of index creates a binary map of all index values, and stores that map in the index blocks, this means that the index will require less space than the B-Tree index. Each bit in the bitmap corresponds to a possible rowid. If the bit is set, then it means that the row wi...
Oracle defines two types of indexes: the B-Tree (Balanced Tree) Index and the Bitmap Index. B-Tree Indexis the default Oracle index created whenever we use the CREATE INDEX command. It compiles a list of values divided into ranges and associates a key with a single row or range of row...
the optimizer will try to use some boolean combination of those particular bitmap indexes. The syntax of INDEX_COMBINE is INDEX_COMBINE(table index).
the optimizer will use on the table whatever boolean combination of bitmap indexes has the best cost estimate. If certain indexes are given as arguments, the optimizer will try to use some boolean combination of those particular bitmap indexes. The syntax of INDEX_COMBINE is INDEX_COMBINE(table...
/*常用语法*/CREATE[UNIQUE | BITMAP]INDEX[schema.]indexnameON[schema.]tablename(column,….);DROPINDEXindexname; 3. CONSTRAINT 约束 官方描述:Use a constraint to define an integrity constraint—a rule that restricts the values in a database. ...
Syntax:BATCH_TABLE_ACCESS_BY_ROWID ( [ @ queryblock ] tablespec [ tablespec ]... ) Description: The BATCH_TABLE_ACCESS_BY_ROWID hint instructs the optimizer to retrieve a few rowids from the index, then access the rows in data block order, to reduce accessing data block times . SQL...
Note that a function-based index can be a btree or bitmap index. Oracle function-based index example The following statement creates a function-based index based on the UPPER function: CREATE INDEX members_last_name_fi ON members(UPPER(last_name));Code language: SQL (Structured Query Language...
select /*+ index(scott.emp,dept_idx) */ * from emp 注意:如果你没有正确的指定Hints,Oracle将忽略该Hints,并且不会给出任何错误。 hint被忽略 如果CBO认为使用hint会导致错误的结果时,hint将被忽略,详见下例 SQL> select /*+ index(t t_ind) */ count(*) from t; ...
non-unique index generally Inlist iterator and union all. Nested loop joins Single table, Multi-column index (access/filter, and skip scan) Index-only query (range scan, full scan, fast full scan, index joins) Bitmap access (with multiple bitmaps per key value) Bitmap and / or / minus...
BITMAP_AS_GIN Use btree_gin extension to create bitmap like index with pg >= 9.4 You will need to create the extension by yourself: create extension btree_gin; Default is to create GIN index, when disabled, a btree index will be created PG_BACKGROUND Use pg_background extension to ...